linux-kernel - Re: [PATCH PREEMPT_RT]: On AT91 ARM: GPIO Interrupt handling can/will stall forever

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Date:	Thu, 29 Nov 2007 16:33:39 +0100
From:	"Remy Bohmer" <linux@...mer.net>
To:	"Russell King - ARM Linux" <linux@....linux.org.uk>
Cc:	"Steven Rostedt" <rostedt@...dmis.org>,
	"Daniel Walker" <dwalker@...sta.com>,
	RT <linux-rt-users@...r.kernel.org>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	"ARM Linux Mailing List" <linux-arm-kernel@...ts.arm.linux.org.uk>,
	"Thomas Gleixner" <tglx@...utronix.de>,
	"Ingo Molnar" <mingo@...e.hu>
Subject: Re: [PATCH PREEMPT_RT]: On AT91 ARM: GPIO Interrupt handling can/will stall forever

Hello Russell,

> While I realise that, I'm telling you that the _problem_ is being
> caused by the wrong handler being used.

Okay, I believe you... (someone told me once, Russell is right, and if
you do not believe him, he is still right ;-)

> SA1100 and PXA have exactly the same setup.  They use the correct
> handler.  Why is AT91 special?

This remark is what convinced me :-))

I changed the interrupt handler from the simple_irq to the edge_irq,
and it works...!!
(I added a noop routine for that .ack part, because there is no ack)

I believe I was too focussed on the masking bug in the RT kernel on
the simple_irq() that I did not see that for the AT91 series the edge
type interrupt handler also works... (even better...) What I thought
was 1 single bug in the RT-kernel turned out to be a number of things
together that aren't correct, even for mainline.

So, to come to a conclusion: The masking bug in RT is still there in
the simple_irq path, and masking has to be removed from the simple_irq
code. Also for mainline. AT91 can live without simple_irq.
I think we are in sync again...

I will post a patch for the AT91 later on, after some more testing.

Kind Regards,

Remy
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